The problem of energy conservation has inspired numerous solutions which deservedly have received much attention in recent times. The particular problem of heating large enclosed spaces such as commercial buildings, industrial plants and the like has attracted an especially large amount of attention wherever the comfort of personnel is to be maintained at reasonable cost. Air recirculation within a large enclosed space to be heated is the well-recognized manner of raising the temperature of the low-lying ambient air, it being known since the earliest times that warm air in a large enclosed space rises above cool air and collects near the roof. Numerous solutions to the problem have been advanced over the years, exemplified by the teachings in an article titled "Recirculation as Applied to the Butler University Field House" by John M. Robertson in Heating and Ventilating, July-August (1929), where it is taught how to maintain an athletic building at a comfortable temperature in winter without resorting to ducts to carry away heated air.
U.S. Pat. No. 2,984,416 provides additional details as to a method employed for ductlessly heating unpartitioned interiors of large buildings with relatively low temperature air at about 125.degree. F., recirculated at relatively low velocity but with high volume. More recently, U.S. Pat. No. 4,103,146 discloses a trimodular apparatus for use in winter, which uses upper and lower modules with at least one intermediate module arranged one atop the other and releasably secured together to define a vertical chamber extending through the modules. For summer use air is vented from the building. It is stated that for winter use, the device draws in and discharges air in stratified layers and at a velocity sufficient to establish a generally toroidal flow of air toward the walls of the building. Further, it is stated that this toroidal flow is sufficient to establish a counter toroidal flow in the air above the apparatus. Any recirculation of air, where a relatively large volume of air is being recirculated within an enclosed building, will necessarily provide a generally upward, outward, downward and return flow of air such as is described in either of the foregoing references, among many others. Whether the flow is generally toroidal or not will depend upon the size and shape of the openings through which air jets issue and which are then recirculated.
At relatively low velocities lower than about 300 ft/min, computed as the volumetric flow of air through the area of an orifice, in this instance, the openings or air outlets through which air is blown, the generally horizontal outward flow of air from the air outlets shown in FIG. 8 of U.S. Pat. No. 2,984,416 or FIG. 5 of U.S. Pat. No. 4,103,146, is not obtained unless the air outlets are relatively close to the roof as illustrated in said FIG. 8. The horizontal outward flow illustrated in FIG. 5 of U.S. Pat. No. 4,103,246 fails to draw in quiescent air from near the roof, when the roof is at least twice as high as the outlets are from the floor. This illustration of the heating mode (the "winder mode") leads away from an understanding of the effective operation of the patented apparatus in its winter mode. As already indicated, generally horizontal flow is obtained in U.S. Pat. No. 2,984,416 because the air outlets are relatively close to the roof. In each of the foregoing references, horizontal flow is associated with operation of a recirculator in its winter mode, and leads away from utilizing horizontal flow for summer cooling.
It has now been found that to generate a generally horizontal outward flow of air from the outlet of a recirculator, when the roof is at least twice as high as the outlets are from the floor level, it is critical that air velocity be in excess of 500 ft/min., and that the shape of the outlet be rectangular with the height of the outlet being about one-fourth of its width.
Though there are numerous references which disclose air recirculators, none addresses itself to providing variable velocity and direction of outlet airflow by telescopably adjusting the orifice area of an air outlet with a fixed orifice area. The relevant prior art references contemplate solving the problem of adjusting air flow through an air outlet of fixed cross-sectional area either (a) by varying the air flow capacity of the fan, or (b) providing baffles or dampers on the outlet to damp air flow. Double deflection grilles are uneconomical, and large blade deflectors protrude from the housing which is undesirable because it can be dangerous. Where multiple air outlets are provided, one or more is closed to provide increased air velocity through the ones left open. As applied to an air recirculator of the type disclosed herein, each of the prior art solutions to the problem is an impractical solution.
The practical solution to the problem is to provide a recirculator (i) which can be shipped as an assembly in a standard truck, in a vertical position; (ii) which does not require that the purchaser assemble the recirculator; and, (iii) which can be used in summer as a cooling fan (referred to as a "man-cooler") to blow air directly upon and cool persons working on the floor of the building in which the recirculator is placed. A solution which requires a telescopable outlet hood is a simple and effective way to provide the practical solution. Besides providing a device which can be used advantageously in both hot and cold weather, the telescopable hood permits the unit to be shipped fully assembled. The customer needs to do no more than adjust the hood depending upon the weather outside the building, and connect the device to a source of electrical power to drive the fan.